Ferrell etal
potentiometers



Feb. 9, 1965 R. FERRELL ETAL Re. 25,725

POTENTIOMETERS 2 Sheets-Sheet 1 Original Filevd March 50, 1962 Feb. 9,1965 R. 1 FERRELL ETAI.

POTENTIOMETERS Original Filed March 50, 1962 2 Sheets-Sheet 2 ,526e JZ,24C f6" f5 INVENTORS POTENTIOMETERS Robert L. Ferrell and Wilbur T.Hardison, Riverside,

. Calif., assignors to Bourns, Inc.

Driginal No. 3,105,217, dated Sept. 24, 1963, Ser. No. 183,855, Mar. 30,1962. Application for reissue June 16, 1964, Ser. No. 386,472

19 Claims. (Cl. 3258-174) Matter enclosed in heavy brackets appears inYthe original patent but forms no part of this reissue specification;matter printed in made by reissue.

This invention pertains to potentiometers, and more particularly toimprovements in potentiometers wherein adjustments are effected byrotation of .a screw-threaded worm or wormscrew. Examples ofpotentiometers of United States PatentQ italics indicates the additionsn the general class to which the invention is directed are i illustratedin U.S. Patents Nos. 2,945,198; 2,887,554; and 2,880,293. Suchpotentiometers comprise an elongate arcuate resistance element disposedaroundthe axis of a rotary contact device -that is'rotated eitherdirectly or't v through clutch means by a worm wheel lthat is in turnoperated by the adjusting wormscrew. l

Potentiometers' of the` class here of interest include cases or housingsof generally square plan-form, or` of square shape with one cornerbeveled for convenience in using ilexible-leadrterminals; `and `ingeneral are constructed to utilize' an outer r'rim portion of thehousing for accommodation of mounting-devices such as screws or bolts.In some such instruments' a kset of throughbores or holes is providedvfor mountingscrews, and

' in other such instruments a set of jindentation's around the peripheryis provided for reception of Wires or other fastening elements. As aconsequenceof those characteristics, the interior space allotted to theresistance element is restricted so that a resistance element of onlyrelatively small radius can be used. Further, only substantiallyidentical instruments (that is, those with matching mounting, holes orgrooves and of the Vsaure over-all dimensions), can be stacked andmounted in. face-to-back relationship.

grooves at or near the outer periphery of the potentiometer, andutilizes for reception of mounting or fastening means, a single holethat is disposed at the center of the potentiometer and extendstherethrough from face to back of the instrument. The single mountinghole is preferably and conveniently produced along and around the axisof rotation of the rotary lcontact and Wormwheel, and thus, is not onlylocated in a region of little value within the instrument and thus.permits use of a much longer resistance element, but the hole is alsoso located and such that potentiometers of various sizes and capacitiescan be readily andk economically disposed or stacked together andsecured in place by the same single mounting screw or rod. In providingthe mounting hole, the potentiometer housing is so formed that requisitestrength is pro-vided, and electrical isolation and protection l isprovided for the operating components from foreignmatter and themounting screw or rod. Further, by novel means, the present inventionprovides for posi.- tive limitation of rotation of the rotary contact toa prescribed arc ofgless than one turn, eliminates the extra meansinvolved in provision of a clutch-device, and concurrently positivelyavoids possibility of stripping of teeth from a'wormwheel. These resultsthe invention attains byutilizing as a wormwheel, a bobbin-shaped wheelhaving preferably toothless peripheral anges which` press against orgrip .the thread or screw of the wormscrew and fhence cause the wheel torotate incidentztoQ rotation of vthe wormscrew. The wheel is molded.from a resiliently preferably insulative material, with an integralstop, and is formed to engage and directly rotate a con- 'du`c'tive'contact'device that brushes on a collector ring Additionally it maybefnoted that the" known Jpriorl fart worin-gear adjusted potentiometersVcertain compromises were necessary to avoid stripping of thel teethofthe wormwheel in the event theWormscrew wasoverrun, that is,rotatedbeyond. prescribed limits,

Thus such a potentiometer might on the one hand have a rotary contactthat wasl permitted to be rotated through an 4in- "definite number ofrevolutions in either direction, that is, no stop means were provided.In that typeY of device the potential division drops suddenly from amaximum 'to a minimum or open circuit zero value (or vvice versa)incident to continued wormscrew rotation. Such operation, or th'epossibility of such operatiom is in many cr- -cuits extremelyundesirable. Hence `in otherprior-art "wormscrew-adjusted potentiometerscertain stopA or movelment-restricting means are employed to 'positivelypre- ""7 {clude rotationof-'the rotary contact through a completetioi'neters isnot visible to the'operator of the ',device, continuedwormscrew rotation during an-adjusting operation brings into action thestop means, after which further rotation of thewormscrew in the samedirection must result in damage'such as stripping of teeth from theWormlwheel, unlesswslip-clutch means are provided Thus the alternativechoice inthe compromise'has been to provide usually in the form ofplate-like friction means, presents revolutionn Since the interiormechanismlof such potensuch clutch means.- Provision `of such lclutchmeans,

theV possibility of vthe `clutch slipping without effective Y rotationof the rotary contact, ythus'n'ullifying the adjustment effort.

The .present invention eliminates mounting holes or `and on the arcuateresistance element. Upon 'continued Vrotation of the wormscrew followingarrestment of con-jV tact rotationlby engagement of the stop with anabutment provided in the instrument housing, the wormscrew threadmerelyslips on the inner surfaces of the lflanges. Thus the potentiometer is,functionally, simplerland less complicated' and expensive than theprior-art 'poten-5A. tiometers having clutch devices, while avoiding theaforementioned undesirable feature Vnot those wormscrew-ad'- justedpotentiometers` that donot include clutchrneans.

'Additionally, by placing theV resistance element: adjacent theouterwall yof the potentiometer ihrousingj'and'pr'oviding aheat-receptive 'and heat-transmitting member nat the center of thehousing,` heat-transferfrbmthe potentiometer Ais greatly improved overthat presented by the prior art wormscrew-adjusted potentiometers. Theloperating parts of the potentiometen'comprising essentially aresistance element, contactmmeansywormwheel means and wormscrew means,areV disposed 'in a two-part case or housing that is .formedpreferablyof dielectric material and that is 'preferably' produced by of the`housing with terminal means, kand the remainder of the operating partsbeing disposed inthe coverf'part.

The two parts of. the housing are provided with? interfitting portionsincluding outer Wall. portions through'one of which a driving-headportion of the wormscrew is accessible. The two housing parts, withrespective components assembled therein,y are arranged and adapted to besecured together by adhesive. The adhesive, together leissued Feb. 9,1965 the arcuate resistance element.

' within a predetermined range of rotation.

with seal means provided -for the driving end of the worms'c'rew, permitthe interior of the housing to besealed tor prevent ingress of foreignmatter. Preferably the housing parts are of square plan form; however,as will be evident, other housing configurations may be used.

The invention provides ,for restricting rotation of the movable contactto an arc somewhat less than 360, ythat is, less than one -full turn;and provides stopmeans for that purpose which stop means are effectiveto positively preclude rotation of the contact ott either end ofFurther, without interposition of clutch means between thewormscrew-driven wheel and the rotary contact, the invention providesmeans that permit indefinitely continued rotation of the wormscrew ineither direction, without'harmful results. To the described ends, theinvention providesa toothless wormscreW-driven Wheel positivelyconnected to the rotary contact to drive the latter, the wheel having aralityof potentiometers 'according to the invention, upon i pair ofopposed stifliy resilient circumferential anges i similar to those of apulley and between which flanges a screw-threaded portion of thewormscrew is gripped to provide a yieldable but driving engagement. Thewheel is provided with a protuberance or extension which serves as astop member that is rotatable in either direction into engagement with acooperative stop or abutmentprovided on one of the housing parts,whereby rotation of the wheel'is positively limited to movement Thusupon continued rotation of the wormscrew in either direction the'contactis driven along the resistance element until theA protuberance on thewheel is arrested bythe abutment, after which occurrence the thread ofthe worm- Y in the potentiometer;

screw slips relatively to the anges of the wheel. Sub- VmediateVcorrespondingrotation of the wheel in the'oppo- `-site direction.

Y l ventionis to provide improvements in Wormscrew-ad justedpotentiometers. l

Another principal object of the invention is to provide simpler and moreeffective actuating meansrfor wormy sere'w-'adjusted potentiometers.

Another principal object of the invention` is'to. provide 'moreeffective` and versatile means for mounting wormscreyv-adjustedpotentiometers.

"Another object of the inventionis to provide an improved arrangementofparts in a wormscrew-adjusted potentiometer'whereby a resistanceelement of optimum length may be used.

Another object ofthe invention is to provide a Wormscrew-adjustedpotentiometer having a simple and inexpensive but very effectivewormscrew and wheel arrangement.v Y

lAn additional 'object of the invention is to provide for.wormscr'ew-'adjusted potentiometers a simple and effectivewormsecrew-driven Wheel for actuatingrotatable driven means of vthepotentiometer'.

Another object is to provide a wormscrew-adjusted potentiometer havinggreatly improved heatdissipation characteristics.

Other kobjects and advantages of theinvention will hereinafter be statedor made evident in the appended Y claims or in the following descriptionof an exemplary Thus inA effect the v'wormscrev'v-and-wheel drive is apositive drive until and unless the'pr'otuberance on the `wheel engagesthe stop or abutment, -and `is in 'sequent reverse rotation of thewormsc'rew causes im- FIGURE 5 is a top View of the baseor body part ofthe housing of the: potentiometer vdepicted in FIGURE 1,

`illustrating details of the internal conguration of the Parti FIGURE 6is a top view 4of the base'or body part of the housing -of thepotentiometer depicted in FIGURE 1, with parts supported by the'bodyshown in operating position;

FIGURE'7 is a sectional view of the V'potentiometer depicted in FIGURE 1the section being taken on a plane and in the direction indicated byline 7 7 of FIGURE 1; FIGURE 8 is a face view of a wormscrew-drivenwheel forming a plural-function component of the potentiometerillustrated ,-in FIGURE l;

FIGURE 9 is a side view of the component depicted in FIGURE 8; f

FIGURE 10 is a plan view of a wormscrew comprised in the potentiometerdepicted in FIGURE l;l

FIGURE l1 is a pictorial view of an electrical collector ring comprisedin lthe potentiometer depicted in FIG- URE 1;

FIGUREv 12 is ,a plan View' of an insulator-spacer used FIGURE 13 is abottom view of a resistance element comprised in the potentiometerdepictedin lFIGURE 1,

Withtermination tabs applied, the view being taken in a directionindicated by the arrow E in FIGURE 7;

FIGURE 14 is a plan View of a-rotary electrical conv tact devicecomprised in the potentiometer depicted in 'FIGURE 1; and

FIGURE '15 isa view in elevation of the device depicted in FIGURE l`4.

Referringirst to FIGURE l, it 'maybe noted that the potentiometer,'designated generally by ordinal 10,v isof generally'r'ectangular faceform, and preferably of square plan form. The operatingcomponents of thepotentiom-l 'eter are enclosed in a housing which preferably .comprisestwo` principal-members each of which `preferably isformed'as a `singlemolded part. As shown, the housing includesa cover-part 12 and a base orbody part .14, which partsfhave closelyl interiitting edge portionswhich permit the parts to be adhesively or otherwise secured togetheralong a zone of juncture 10a and along a juncture or zone of contact10b. As will be noted more inl detail later herein, the potentiometerincludes terminals which in the illustrated exemplary embodiment are inthe form of flexible wires or leads and which comprise 4amovable-contact terminal 15 and` first and ysecond resistance-elementterminals 16 Yand 16. Adjustment` o f electrical potential valuesbetween terminal 15 and either y ofthe other terminals is eifected. byrotation of worm-- screw means which comprises a driving head 18hthat inthe exemplary embodiment p rotrudesl from the housing` and is thusaccessible for operation. As will be described more yfull-'yhereinafter, th e .cover part 12 has a preferably cylindrical part orportion 12C, the extremity of which extends through and closelyjts ahole lin body part 14 and mayE-b'e substantially flush withthe surfaceof the body partas shown. The tubular interior of the portion k12cprovides the h ole 10h through Awhich a mounting screw or the like mayextend, as will presentlybe made more evident. i v

i, As is indicated in FIGURE l2 k, seyeral -potentiometers according to.the invention,..and ofthe same sizefor of several sizes, may besupported in face-to-back-relation- Vship onfa single common fasten-ingor mounting device.

As depicted, three miniature potentiometers vP,'a s ,mall potentiometerQ, and a larger potentiometer R, are all mounted upon la single machinescrew S, by which screw and the associated nut N and washer W thepotentiometers are secured to 'one face' of a sheet-like panel T. As isevident, the heads of the vadjusting wormscrews may all be oriented inthe same direction, or otherwise as choice or conditions may dictate.Equally evident is the fact that potentiometers may be disposed inspacedapart relationship `along a common single screw or rod, withspacers, nuts or other clamping means securing the individualpotentiometers in their respective positions.

With attention-directed to FIGURES 3 and 4, the cover part 12 is`preferably formed as an integrally molded member of dielectric material,having a generally rectangular exterior coniiguration defined by a iloor12f and side walls such as 12W. As previously noted, the cover partcomprises a cylindrical part 12c that is centrally located `andperpendicular to the floor 12f, and Whose tubular interior provides themounting hole h. Disposed through a suitable bore formed in one wall ofpart 12 is the wormscrew 18, theinner end 18eof which is disposed forrotation in` a groove y12g formed in a buttress provided adjacent oneVcorner of the part. The wormscrew (FIGURES 3, 4 and 10) is provided witha shoulder 18s upon which is received a sealing O-ring 19 (FIGURE 4)',which ring is also received in a step-portion of a properly shaped bore12b formed in the sidewall of part 12. The wormscrew is retained inposition with the indicated bearing surfaces thereof seated in Ithelbearings provided by the bore 12b and groove 12g, by -a retainer pinl20 (FIGURE 3), which retainer pinv is received in a well or bore .incover part 12 as indicated and which isthus disposed in4 tangentialengagement with the wormscrew within a circumferential retainer groove18g formed iadjacent the head of the wormscrew as shown.

The wormscrew is adapted to engage and induce rotation of a wheel 22(FIGURES 3, 4, 7 and 9). To that end the wormscrew 18.comprisesa' wormor threadl 18t that is received between and engages portions of theinner faces of opposed resilient flangesf22f, 22f of wheel 22,as isindicated in FIGURES 3 Vand 7.v The thread 18t is preferably produced oflen-gth such that the end portions'thereof both engage the inner facesof the iianges.

f Thus asillustrated, the thread does not extendbeyond theconriesof thegroove 22g of wheel 22. Further, to provide an effective drivinginterengagement of the thread 18t with the flanges of wheel 22, Vtheoutside effective diameter of theA thread is made slightly greater `thanthe perpendicular distance between the Vinner faces' of the flanges,whereby the flanges are, in thexvicinityof the zone of interengagement,slightly sprung Yapartand thus caused to firmly grip the thread. `Thewheel 22 is thus preferably madey of:al suitable tough slightlymesilientsynthetic resin or' polymer, of which a material marketed under the.tradel name Nylatron GS-by TheV Polymer Corporation of Reading, Pa., iseminently suitable. While herein :illustrated 'as comprising two opposedlianges, it is suicient in certain cases to form the wheel 22 withbut15a single ange for engagementfby the, thread of thev lated toarotatable -contact device whose function isto provide electricalinterconnectionbetween `any selected portion of a contact: area of aresistance element, anda conductive collector ring. vThe contact device24 (FIG- tact alloys. The preferred contact device, Vas illustrated, isformed as `an integral or single-piece element or part, and has acentral opening or `aperture 24a of a size to permit closelyl controlledrotation upon and about cylinder 12o. The contact device, herein termed,the contact inthe interest of brevity, is provided with a notch 24u inwhich is received a driving nub or key 22k that is attached to or formedintegrally with the body of wheel 22 (FIGURES 8 land 9). As is indicatedin FIGURE 3, the opposed horns or edges of the contact at opposite sidesof notch 24n are tightly received in respective slots (such as 22z,FIGURE 9) formed by -respective overhangs or eaves such as 22e providedas integral parts of the key 22k. The contact is thus readily attachedto wheel 22 before the Wheel isv mounted on Vcylinder 12e; and when thesubassembly comprising the wheel and contact is mounted on the cylinderthe contact is constrained to rotate with the wheel. The extent ofrotation or angular traverse of the wheel 22 (and consequently also ofthe contact device 24) is limited by -a stop or abutment 12sy (FIGURE 3)that is provided in cover 12 preferably as `an-integral part of thecover, and which abutment is disposed in Vthe path of kstop means whichcomprise one or more extensions or stops 22s (FIGURE 8) each formed `asa radial protuberance extending outwardly in the general plane of one ofthe flanges of the wheel 22. The stop means thus provided on `the wheel22, and the abutment means 12s provided in the cover 12, are sodimensioned that the contactrpoint next to be described may not bedriven beyond either end of theresistanceelement with which itcooperates. Thus those dimensions are related to theangular extent orlength of the resistive part of the resistanceelement. f The contactdevice 24 (FIGURESVM and l5) is sheared along an arcuate zoneor line`A242/.,V to provide a flatbase 24bof 360 extent for supporting contact,or bearing, on wheel 22 and for proper rotational cooper-ation with thecylinder 12e, and to provide a divergent '011twardly extending resilientlimb 24s preferablyvof arcuate confguration'integral at its ends withthe base 24h. As is illustrated in FIGURE l5, the limb 24s is deformedadjacent its junctures with thebase 24h, so as to diverge or extend awayfrom the plane of base 24h, whereby to permit the limb to yieldand toexert a force effective to maintain the contact pointin-effective-electrical communication with the Vresistance element, Thecontact point, 24e, is provided on a radial extension of limb 24s,eitheras ai pellet of precious :metal fusion-united to the limbextension, or, as i illustrated, as .a protuberance formed bydeformation or Vdimpling of the extension.

The cover 12 is provided adjacent its corners with a set of indentationsor recesses such as those illustrated at 12m, 12h (FIGURE 3), whichrecesses are shaped and disposed to receive key-pins such as thoseillustrated at 14m, 14n (FIGURE 6)*gformed `as upstandinglprotuberances`attached to or formedintegral with, housinggbody 14. The key-pins-'arethusfadapted to precisely/,position the cover on the body parti14. Asisevident fromexamination ofFIGURE 5, the housing body part 14 is formedto provide a trou`gh-like generally ,annularwrecess "14rthatfis partlyencircled by anupwstanding wall 14W.

The' recess opens at'onefffside-of the body part to provide space forplacement of terminal means tofbepresently described, the-wall beingmodified at' that side-by pro- URES 4, 14 and l5) is, `for theillustrated exemplary form fof the potentiometer, formed by a shearingand stamping operation, from a sheet of resilient conductive materialsuch as one of the commercially-available con-- vision of outwardlyextending channels 14k asindicated. The part 14 also 'comprises acentrally disposed upstanding circular wall 14V the inside diameter ofwhich is such as to provide `a close t around cylinder 12c ofthe coverpart Y12, .as is indicatedin FIGURE 7. Thellatter ligure makes evident'the fact that after the' twoohousing parts var'e brought into matingcontact, they may be adhesively secured and-sealed together along theexterior1 juncture 10a and in .the zone between cylinder 12e yand wall14V.

Disposed in-'recess -14r,a's is indicated inFIGURES 4611a1' 1d."'7,`isanY arcuate elongate lresistance element 25 which in the illustratedexemplaryembodiment of 'a potentiometer is in the configuration ofvasection of a toroid. The resistanceelement compriseses'sentially amandrel or core -25c upon which issupported a resistive means 25W whichin the exemplary embodiment is a coil or winding of resistance wire theconvolutions of which are laterally mutually insulated each from theothers.

The core may be an insulated member of metal, or a` member formed ofdielectric material such as anvinsulative ceramic. The resistanceelement' is preferably spaced from the iioor of recess 14r by aninsulative spacer member 26 (FIGURE 12), so that diiferent types ofterminals (iiexible, pin in base, or pins horizontal) may be provided.As illustrated, exible-wire terminals are provided. As is indicated inFIGURE 13, the resistance element 25 has physically secured thereto andelectrically connectedto respective end portions of the resistive means,lirst and second termination tabs or strips 25t and 25u that are, in thecase of the' wire-type resistive means shown, fusion-unitedwithrespective end portions of the wire as by brazing or-welding. Thestrips25t and 25u are disposed below the resistance element in recess14r, in complementary recesses 14e, 14f formed in the floor of body part14 (FIGURE 5); and each strip has secured thereto a respective terminalwhich in the illustrated embodiment is a respective one'of Wires 15, 16.

y By'the described means, excellent accurate electrical connections tothe ends of the resistance element are provided. Disposed upon the uppersubstantially circular end face of wall 14V of body part 14, is anexposed conductive resilient collector ring 28 (FIGURE 11). Thecollector ring is deformed or bowed upwardly so as to present yieldinguppermost contact areas 28a, 28a each diametrically opposite the other,and to present two diametrically opposite areas 28h, 28h to rest uponwal1'14v. Ring 28 is provided with a terminating means 28t preferably inthe form of an integralstrip which is formed to depend from the ring andlie against the wall l14V in recess 14r. Means'28t is electricallyconnected (as by brazing or welding)to athird terminal device, whichdevice'in the illustrated embodiment of a potentiometer is wire terminal15. The latter terminal is disposed in the bottom of one of recesses 14kprovided in the oor of part 14, as depicted in FIGURE'6.

` Subsequent to assembly-"of spacer-26, resistance element 25, collectorring 2,8, and the respective terminal devices, in body part 14, thoseparts are secured in place of theV pin of a next-adjacent potentiometer.As isevident, a panel lmay similarly be provided With a hole, or `a pin,properly disposed for cooperative action with Vthe opposite member of amounted potentiometer. As is evident, where such a projection isprovided and is not desired in a particular application of thepotentiometer, the projection may be easily removed, as by scraping,abrasion or cutting.

As is evident, rotation of the wormscrew 18- (as by a tool applied tohead 18h and'rotated), firstinduces rotation of wheel 22 and contactdevice 24 until engagement of the aforedescr'ibed Stop means 22s withabutment 12s occurs, after which any continued-rotation ofthewormscrew-in the same direction merely results in slippage of thescrewthread of the wormscrewrelative to the flange or ilanges of wheel22. Thereafter, wormscrew rotation in the opposite direction causesimmediate reverse rotation of the wheel and contact. Also it is evidentthat multiple stacking of potentiometers of the sam'esize or of-dicerentsizes upon a single mounting .screw will not interfere in any Way withoperation ofeither of the potentiometers thus mounted. Further, in thosecases where pin terminals extending downwardly throughthe body part areused in lieu of the wire' terminals. shown in the preferred embodiment(in which case multiple mounting maynot be practical and wherein in factthe potentiometer may be mounted by its-terminal pins) 'the advantage ofa ,muchv larger than usual resistance element still accrues to theydisclosed potentiometer. Thus it is evident that the aforementionedobjects of the invention are attained.

It further is evident that in the light of .thef'present' disclosure indetail of an exemplary potentiometer embodying'the invention, changesand modiiications will occur to those skilled in the art, andaccordingly 'it is not desired to limit the invention to the particulardetails of the exemplary structure disclosed, other than as'theyare byadhesive-means such as insulative encapsulating or` potting compoundonly a small portion of which is in-y sive. Additional compound oradhesive may bev applied as necessaryvto insure complete closure-of theopen side of kbody part 14. A s the two housing parts are broughttogether, cylinder `12 is entered into the central opening in body part14, and one housing part rotated relative to the other (if necessary) tobring key 14m into line 'withl its mating recess, and the parts arepressed together. In that action, Contact point Z4cengages the exposedsurface ofy the resistive means of' the resistance element and points28aof the ring 28 engage the base -24b of the contact, the springportions of those elements'yieldin'g and providing good contact. 'IlWhi.lenot'e`ssential, the housing'parts may 'be provided with means forfacilitating stacking vand/ or prevention of 'rotation upon thecentrally disposed mounting screw. To v`that end, properly disposedprotruding projections orpins .suchfas 14X (FIGURESl and `4) maybeprovided on one-ofthe' housing parts, andcomplement'ary sockets.(notshovtln).formed-in.the` other :housingpart for reception speciiicallydefined in'the appended fclaims.

We claim: `1. A wormscrew-adjusted potentiometer comprising:

u "first means, comprising a box-like housing having iirst "secondmeans, comprising 4adjustable potentiometricV 55 means disposed in saidVhousing around said structural ymeans and comprising means mounted forrotation on said cylindrical bearing surface, and said :second meanscomprising terminalmeans 1for said vpotentiometric means; and thirdmeans, lcomprising wormscrew means `supported by'said housing andexposed-for rotation by means exterior of saidhousing, said wormscrewmeans beingiconstructedand arranged with a wormscrew thread in drivingengagement with said second means for effecting adjustment thereof in`response to rotation of said wormscrew means. 2. A wormscrew-adjustedpotentiometer as 'defined in claim 1, said second means comprising aflanged wheel rotatable on said cylindrical bearing surface and amovable contact rotatable byl said wheel, .said Wheel'having -berintegralfwith one of. saidtirst and secondV portions,

and said wheel being constructed andv arranged to rotate upon saidtubular portion. 4. In a ywormscrew-adjusted potentiometer, first meansincluding potentiometric means including an arcuate resistanceV element,and means including a rotary'contact therefor;

second means, comprising wormscrew means having a screw thread;v thirdmeans, comprising a toothless wheel having a circumferential radialflange, an annular substantially fiat radial face 'of which flangepresses against said screw thread to be frictionally driven therebyincil dent to rotation of the wormscrew means, and means connecting saidrotary contact to said wheel to be driven by the latter; and fourthmeans, comprising housing means constructed and arranged to support saidfirst, second and third means. 5. The combination vdefined by claimV 4,said potentiometric means comprising a rotary contact device rotatableby said wheel and further comprising an arcuate comprising aflvoorlportion and encircling marginal I portions anda' centrally-disposedportion including an upstanding tubular portion,vand said second. parthaving a portion-providing aYcentrally-located aperture closelyencircling said centrally disposed portion of saidffirst part, wherebyto provide a mounting-hole for the'potentiometer therethrough from faceto'face; v second means, comprising'anarcuate resistance" elementdisposed in said housing and substantiallyl encircling said tubularportion, and Afirst and second terminal means connected to respectiveends of said resistance element and each extending through to theexterior of said housing; i third means,comprising a rotatable contactdevice constructed and arranged to rotatewabout said tubular portion and'having' first and second contact portions the tirst of which isdisposed forwiping contact on said resistance element; fourth means,comprising av conductive -collector encircling said tubular portion andarranged to be conductively wiped by said second contact portion, andterminal means connected to said collector and extending to the exteriorof said housing; and fifth means, including a rotary wheel disposed forrotation about said tubular portion and engaging said contact device forrotating the latter, and a wormscrew carried by said housing and exposedto the exterior thereof and engaging said rotary wheel for rotating thelatter; whereby said potentiometer or a plurality thereof may be mountedupon and secured in fixed position by a single'mounting device extendedthrough the centrally-disposed hole therethrough, and whereby any suchpotentiometer may be adjusted'by rotation of the wormscrew thereof. 7. Apotentiometer yaccording to claim 6, said first and second parts of saidhousing being of substantially square plan form, and said resistanceelement spanning from wall to Wall inside said housing.

8. A potentiometer according to claim 6, said rotary wheel having aperipheral groove and being of pulleylike conformation with opposed rimflanges at least one of which is resilient, and lascrew-thread portionof' said Wormscrew being kdisposed between said flanges for fric Wheelcomprising a peripheral protuberance on at least one of said flanges,and said housing comprising an inwardly extending abutment constructedand Varranged to be engaged by said abutment to limit rotary movementsof said rotary` wheel. Y

10. A potentiometer' according to claim 8, said rotary. wheel being' ofresilient dielectric material and having an upstanding anchor on one ofsaid anges, and said rotatable contact device being of conductivematerial of generally circular plan form with said first contact pointprotruding from the periphery thereof and having portions forming Va:notch engaging said anchorto lsecure the said Contact device to saidrotary wheel.

ll. A potentiometer according to claim 8, said Wormscrew having a threadportion both ends of which engage the inner opposed faces of; the rimanges of said rotary wheel.

' 12. In a wormscreW-adjusted potentiometensthe combination comprising:t

housing means, including first and second housing mem# bers ofsubstantially Vsquare plan-form and having respective first and secondsubstantially flatparallel faces and having portions defining acentrally disposed aperture therethrough perpendicular to said faces,said housing members being complementary and forming a tubular structuredefining at least a part of .Y said aperture;.and together providing aninternalV cavity; Y n 1 `wormscrew means Vincluding fa--Wormscrewrotatably mounted in said housing means and `having a screw 5 portionexposed at the interior of said cavity and "havinga driving endaccessible from the exterior of said housing means;y v -rotary wheelvmeans in said cavityand mounted for rotation 'about said tubularstructure and engaging said screw portion` for-rotation incident torotation of said Wormscrew means; t conductive `rotary.,contact meansconnected tousaid wheel means for .Y rotation therewith, said contactmeans comprisinginner and outer contact areaselectricallyinterconnected; Y `resistance element means disposed in saidcavityiand 1 substantial-ly encircling said tubular structure and v vhaving an arcuate exposed area arrangedi to be wiped by said outercontact area4 incidentv to rotation of v 'said'rotary wheel means; vconductive collector means'substantially encircling said ,tubularstructure and disposed for wipingv engagement with said inner contactarea `of said rotary contact means; and telectrical means, includingterminal devices attached and'connected to respective ends of saidresistance element means, and a terminal device connected to saidcollector means, said yterminal means extending from within said cavityto the exterior of said hous-V ing means.

13. The combination definedby claim 12, said'rotary wheel means being offiat bobbin-shape having outwardly directed peripheral flanges at leastone of which is resilient, and said lianges clasping and Wormscrew meansfor driving engagement therewith.

Y 14. The combination defined by claim v13, saidrotary wheelmeans havinga peripheral protuberance and said housing having an abutment disposedfor coaction with said protuberance-to limit rotation of said wheelmeans when said wheel means is overdriven by said wormscrew means, saidwormscrew slipping relative to said wheel means when overdriven withrotation of the said wheel means prevented by said abutment. Y

15. The combination defined by claim 12, said first housing memberhaving a centrally'disposed'itubular portion' providing saidcentrally-disposed aperture, vand said lar structurek disposedinconcentric relation with respect to the'saidtubular portion, and means.adhesively securing said housing members together.

16. Thecombination defined by yclaim 12, said resistance element meansbeing secured to said second housing member in said cavity, and saidcollector being in the form of a'iiat ringdisposed `on the end of saidtubular structure and substantially concentric with said resistanceelement.

17. For a potentiometereof the type comprisingas func-v tionalcomponents an arcuate elongate resistance element, rotatable contactmeans having a contact in wiping relationship-with the resistanceelement, a screw-threaded shaft, and a rotary element rotatable by thescrew'-v threaded shaft and secured vto said contact means for rotatingthe latter, improvements in housing and supporting means comprising rstand. second housing: members, said rst member comprising a floor portionpresenting a fiat exterior face [and 'encircling upstanding wallportions integral therewith and a centrally-disposed upstanding tubularportion perpendicular to said'face and disposed inwardly from said wallportions, and said second member having a'portion providing a flatsurface encircling a centrally disposed aperture axially aligned withand closely receiving said tubular portion of said rst member, and saidsecond member and said first member being disposed with said facessubstantiallyparallel and having interengaging portions at said wallvportions whereby to provide a box-like housing having :acentrallydisposed aperture therethrough,] having a centrally disposedaperture, and said second member comprising a portion providing a Vfiatexterior face disposed generally parallel to vthe flat exterior rface ofsaid .first housing member and having a centrally disposed-aperture,Vsaid first'and second housing members comprising portions forming aplurality of exterior wall portions 4each extending between therespective` flat exterior faces of said first and second housingmembers, and lsaid `rst and second housing members comprising agenerally tubular portion around the respective said aperturesandextending betweenthe respective flat exterior facesof said first andsecond housing members, whereby to :formi a generally box-like housinghaving a centrally disposed tubular portion providing 'amounling'aperture through said'housing from one to the other ofthe -saidflat exterior faces of thek said first and second housing members andproviding am enclosed generally to'roidal space around said generallyvtubular portion, and said frstand second Yhousing membershavingtinterengaging portions to, .permit sealing `of Tsaid `fspace 1against ingress'ofeforeign: 1

matter, and said housing being yconstructedand arranged to housegsaidfunctional components, whereby said potentiometer can bemounted andatlixedin spatialv posi# tion ron' a single rod-like mount.

18. Improvements according to claim 17, said-housing members beingofsubstantially'square planvforrn.- 19. Potentiometric means comprising:v rs't.means,iincluding housing 'means presenting rst .and secondopposite faces at least one of which is dat, -said ,housingmeansincluding means providing 11a centrally-located hole th'erethrough'fromface to face thereof .for reception of a mounting screw ortl1e.1ike,;said last-named means comprising generally tubular meansaround said hole adapted tobear z-compressive .stress applied tosaid-housing means nemounting the'latter; second means, including rotarymeans including potentiometer vcontact means rand wheel means, disl i:.posed for rotation [0111 abou-tsaid vtubular means in'said housingmeans; Ythird means, including resistance-element means in said vhousingmeans, disposed aroundsaid tubular means and spaced radially outwardlytherefrom and constructed and arranged to be brushed by said contactmeans; andl lfourth means,.comprising wormscrew means including ascrewthread exposed in said housing in driving enl gagement with saidrotary means, ywhereby said potentiometriemeans may be mounted upon asingle mountingelement yand may be adjusted by rotation of saidwormscrewtrneans;

References Cited the Examiner The following references, cited bytheExaminer, are of' record inthe patented lile'of this patenteor theoriginal patent. n l UNITEDSTATES PATENTS RICHARD: M. woon, PrimaryExaminer.

